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Q8.4.1

Fabrication and Characterization of Iron-Cobalt Alloy Magnetic Nanocluster Wires by Thermal Decomposition Method in Magnetic Fields

Heesung Moon, Changhun Nam, Changwook Kim†, Bongsoo Kim* and Gangho Lee1 Department of Chemistry and School of Molecular Science – BK21, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Korea † Also with Technology division, Samsung SDI company, Limited, Suwon, 442-390, Korea. 1 Department of Chemistry, Kyungpook University, Daegu, Korea

ABSTRACT

We present one-step synthetic method of magnetic alloy nanocluster wires. This process is simple, less expensive, and saves time. The gas is vaporized in a vacuum chamber from a solution of dicobalt octacarbonyl (Co2(CO)8) and iron pentacarbonyl (Fe(CO)5) mixture, and thermally decomposed by using a nichrome wire. The silicon substrate is placed in a homogeneous magnetic field which is produced by two permanent magnets (4000 gauss), so that the nanowires easily grow in the direction of the magnetic flux. From X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM), we confirmed that these have a body-centered-cubic (BCC) structure with the magnetization easy axis of [110] direction, and a diameter in the range of 4 to 6 nm with a few micrometers in length. Also, we investigated that the squareness of the hysteresis loop is 61% for magnetic fields parallel to the wires and the coercivity along the easy axis is 670 oersteds by using vibrating scanning magnetometer (VSM).

INTRODUCTION

One dimensional nanostructures show fascinating characteristics in optical, electronic, mechanical, and thermal properties [1]. Especially, magnetic nanowires have attracted a great deal of interest for their potential use as nanoscale building blocks in the emerging field of spintronic devices. Spintronics or magnetoelectronics, the concept using the alignment of the electron spins, would be a breakthrough for the existing information technology [2]. The

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Q8.4.2

perpendicular magnetic alloy nanowires are advantageous for high-performance applications such as the high density magnetic storage device, where a single nanowire can be used as only a bit [3]. Iron-cobalt (Fe-Co) alloys are important soft magnetic materials because of high saturation magnetization and low coercivity [4]. Therefore they can be useful for high-density magnetic recording. These are mainly made by electrochemical deposition using template [4, 5]., It is, however, difficult to separate the product from anodic aluminum oxide template and the yield is relatively very low. In a recent work, ferromagnetic iron (Fe) and cobalt (Co) nanocluster wires are simply fabricated by using permanent magnet [6]. In this paper, we demonstrate the perpendicular Fe-Co alloy nano